Gas pipeline systems that distribute natural gas through pipeline systems require a network of compressor stations to maintain the appropriate flow of gas through the pipelines. Depending on the flow requirements and the pipeline layout, compressor stations are required at various intervals and at specific locations in the pipeline system. Compressor stations are designed both to compress the gas within the pipeline as well as to remove the heat generated from compressing the gas. Gas is compressed utilizing known compressing equipment and cooling equipment. Generally, the heat of compression is managed by driving cooling air over the compression equipment and piping using large air circulation fans.
A by-product of the compression equipment and the cooling fans is that significant noise is generated by both the compression equipment and the cooling fans. In that compressor stations may be located in both relatively isolated locations but also in densely populated areas, the management of noise in and around compressor stations is becoming increasingly important to comply with local laws concerning noise.
More specifically, the compressors are usually driven by a gas engine, sometimes by a turbine, and in some cases by an electric motor. The gas engine, turbines, and the compressor are very loud noise sources, often exceeding 105 dBA and in some cases up to 120 dBA. Traditionally, these loud noise sources are contained within a building that usually has very poor acoustical and ventilation properties. The large electric motors also have noise issues, primarily on the ventilation air supply and exhaust.
In the past, noise suppression for gas compression stations has been dealt with in a reactive manner following an identified noise problem. That is, a gas compression station is built and only after complaints or a clear noise problem is identified is the building modified and the cooling fan silenced to address the noise problem. This approach is both costly and inefficient because the collective issues of gas compression, heat management and noise suppression are not addressed from an integrated perspective at the time the compressor station is built.
That is, compressor stations are designed primarily to provide appropriate gas compression and heat management, but the noise issue is addressed only after the design of a station and only when due to the location of the station has noise been identified as a problem. The result is that in order to address an identified noise problem, massive and expensive noise suppression equipment is retroactively fitted to an existing compressor station. Moreover, in that most compressor stations are different both in terms of the physical dimensions of the buildings and their requirements for handling different volumes of cooling air, the retroactive approach to an identified noise issue is both complicated and inefficient given that different stations will require very different designs to retrofit noise suppression equipment.
Typically, the most costly and difficult noise source to manage is the fan noise of the very large coolers used to cool the compressed gas (and often, the engine casing's glycol/antifreeze). Common sizes of fans are fans having diameters of 4 feet to 13 feet. Typically, an 8 foot fan generally requires 20–25 HP to deliver approximately 80,000 SCFM and would be mated up with a 600 HP compressor engine. A 13 foot diameter fan would require 50–57 HP and would deliver approximately 250,000 SCFM and would be mated up with a 1400 HP engine. Significant noise levels can result from operating such equipment at these horsepower levels.
A further problem or inefficiency is that the cooler fans are usually driven by a jackshaft connected to the main compressor engine. Thus, the cooler fan is not only a major noise source but it is also utilizing power from the compressor engine, typically in the order of 4% of the energy required to run the compressor.
In some cases the fans are driven by an electric motor. The inlet and the outlet of the fan as well as the cooler's plenum walls are major noise sources that usually demand noise suppression.
In recent years, stricter environmental laws require that the oil and gas companies suppress the noise of their facilities to within permissible noise level limits.
Further still, the current practices of retrofitting compressor buildings with noise suppression equipment may result in problems of equipment overheating if the noise suppression equipment does not adequately address the issue of heat management. That is, the design of noise suppression equipment may decrease the heat transfer capabilities of the building as a whole with the result that under certain climatic or seasonal conditions, equipment will overheat requiring that operators increase ventilation within the building by opening doors with the result that noise suppression is compromised and noise will emanate from the building.
Accordingly, there has been a need for an integrated system for compressor stations that effectively addresses the need for both heat management and noise management.
In addition, there has been a need for a modular design of such a system to enable the efficient construction of such systems.